Magnetic switches



H. REIFEL MAGNETIC SWITCHES July 11, 1961 Filed May 4, 1959 Ill UnitedStates Patent 2,992,307 MAGNETIC SWITCHES Harry Reifel, Waltham, Mass,assignor to Stevens- Amold Inc, a corporation of Massachusetts Filed May4, 1959, Ser. No. 810,776 4 Claims. (Cl. 200-90) This invention relatesto magnetic switches having cantilever supported, vibratory reeds.

Magnetic switches having cantilever supported reeds of spring metal arewidely used as choppers and relays. Such reeds are deflected by magneticfields set up by flow of current through associated coils, and usuallybear contacts which touch other stationary contacts. Since the contactson such reeds move in circular arcs having centers at the fixed ends ofthe reeds, there is rubbing wear between the movable and fixed contacts.Such contacts may be of precious metal such as gold or platinum, and therubbing wear to which they have been subjected has required frequentservicing of the contacts.

For reducing the wear of the contacts, I remove them form the reeds andplace them on contact lifters of spring metal which are moved by thereeds, and which are so shaped and arranged that there is no rubbingwear between the contacts they bear and the fixed contacts. This stillleaves rubbing wear where the contact lifters touch the reeds, but Ireduce the friction between such rubbing surfaces by coating thesurfaces of the reeds where they are in rubbing contact with the contactlifters with a dry lubricant such as tetrofluorethylene. Such alubricant does not adhere to the contact lifters as all previously triedlubricants have done, and has no adverse eifect upon the operation ofthe switches.

Using these two features, the life of a magnetic switch of this type hasbeen greatly prolonged, and its maintenance greatly reduced.

An object of this invention is to reduce the rubbing wear in a magneticswitch having a cantilever supported reed.

Another object of this invention is to reduce the friction between therubbing components of a magnetic switch having a cantilever supported,contact actuating reed.

This invention will now be described with reference to the annexeddrawings, of which:

FIG. 1 is a top plan view of a magnetic switch embodying this invention;

FIG. 2 is a side view of the switch;

FIG. 3 is an enlarged fragmentary view of the switch showing thecoatings of dry lubricant on the reed surfaces opposite the contactlifters, and

FIG. 4 is a fragmentary bottom plan view of the switch.

A metal base has one end portion with reduced width to which are clampedby a bolt 11, a pair of metal blocks 12 which extend above and below thebase on opposite sides of said end portion. Above the base 10, there areclamped between the tops of the blocks 12, insulating spacers 13 next toth blocks 12, metal spacers 14 next to the spacers 13, the outer ends ofmetal plates 15 next to the spacers 14, the outer ends of metal contactstrips 16 next to the plates 15, metal spacers 17 next to the strips 16,insulating spacers 18 next to the spacers 17, metal spacers 19 next tothe spacers 18, the outer ends of metal contact lifters 20 next to thespacers 19, and the outer end of a reed 21 of non-magnetic, spring metalbetween the outer ends of the contact lifters 20, the reed beingcantilever supported at its outer end.

Below the base 10 and between the lower ends of the blocks 12 is aspacer block 23, the previously referred to, reduced width base portionbeing above the block 23.

The contact lifters 20 have inner portions 24 which curve from andtowards the reed 21, and which have at their inner ends, contacts 25which are U-shaped in section, and between the legs of which extend theinner ends of the contact strips 16. Contact spacing bolts 26 arethreaded into the plates 15 with their inner ends in contact with thecontact lifters 20, and are used for adjusting the spacing between thelegs of the contacts 25 and the inner ends of the strips 16.

The reed 21 has attached to its free outer end portion by staples 26,laminar reeds 27 of non-magnetic spring metal which extend in contactwith opposite sides of the reed to adjacent its fixed end, and straps 28of magnetic metal in contact with outer end portions of the reeds 27 onouter sides thereof. The straps 28 have flanges 29 extendingapproximately parallel to and spaced from the top of the base 10. Thebase 10 has a slot extending along the longitudinal center of its otherend in which is fitted a permanent magnet bar 30 under the magnetic tomagnetic field changes at the pole pieces 35. Attached to said other endof the base 10 by machine screw 32 and clamp plates 33 is anelectromagnet 34 which has pole pieces 35 which are bent inwardlytowards the free end of the reed, with their inner ends spaced apartopposite the free end of the free end of the reed. One of the blocks 12has a terminal lug 37 attached thereto.

Where the inner ends of the contact lifters 20 would otherwise rubagainst the opposite sides of the laminar reeds 27 when the reed 21 isvibrated, there is applied to such opposite sides, coatings 40 of thedry lubricant tetrofluorethylene which greatly reduces the rubbingfriction between such reed sides and the contact lifters.

In operation, assuming the device is operating as a chopper, alternatingcurrent applied to the electromagnet 34 would change the magnetic fieldat the magnetic straps 28 on the free end of the reed 21, causing thereed to vibrate. The inner ends of the contact lifters 20 are in contactwith the coatings 40 on the laminar reeds 27, and are deflectedoutwardly by the vibration of the reed, moving during a first halfcycle,one contact 25 outwardly, and moving during the second halfcycle, theother contact 25 outwardly. The outward movements of the contacts 25cause them to break contact with the outer ends of the contact strips16, opening previously closed circuits connected to the contact lifters20 and the contact strips 16.

The contact making surfaces of the contacts 25 and of the contact strips16 would be gold or platinum, and by using the lifters 20 instead of thereed directly, to make and break contacts, rubbing wear of the contactsurfaces is greatly reduced.

By using the lubricating coatings the reed laminations 27 where thecontact lifters contact such surfaces, the rubbing friction betweoen thereed surfaces and the rubbing lifter surfaces is greatly reduced,resulting in increased life and decreased maintenance.

Electrical terminals which are not shown, would be provided for theelectromagnet 34 and for the contact lifters 20 and the contact strips16.

The base 10 is designed to take one reed assembly, one contact assemblyand one electromagnet as shown by the drawings, or to take another reedassembly, another contact assembly and another electromagnet which wouldbe placed, looking at FIG. 2, above the base 10.

The coatings 40 are insulators so that electrostatic voltages aregenerated by their rubbing contact with the contact lifters. Thesevoltages, however, are shorted out by the reed 21 being directlyconnected to the contact lifters 20 where they are supported.

40 on the surfaces of What is claimed is:

l. A magnetic switch having a cantilever supported reed of spring metal,means including an electromagnet for vibrating said reed, said reedhaving a contact lifter deflecting surface, a cantilever supportedcontact lifter of spring metalhaving a surface opposite said surface, alayer of tetrofluorethylene lubricant on one of said surfaces in contactwith the other of said surfaces, a contact surface on said lifter, andmeans providing a fixed contact surface opposite said contact surface.

2. A magnetic switch having a cantilever-supported reed of spring metal,means including an electromagnet for Vibrating said reed, said reedhaving a contact lifter deflecting surface, a layer oftetrofluorethylene lubricant on said surface, a gantilever supportedcontact lifter of spring metal having a surface in contact with saidlayer, a contact surface on said lifter, and means providing a fixedcontact surface opposite said contact surface.

3. A magnetic switch having a cantilever supported reed of spring metal,means including an electromagnet for vibrating said reed, said reedhaving a contact lifter deflecting surface, a cantilever supportedcontact lifter of spring metal having a surface opposite said surface, a

4 layer of tetrofiuorethylene lubricant on one of said surfaces incontact with the other of said surfaces, means directly connecting saidreed and lifter electrically together, a contact surface on said lifter,and means providing a fixed contact surface opposite said contactsurface.

4. A magnetic switch having a cantilever supported reed of spring metal,means including an electromagnet for vibrating said reed, said reedhaving a contact lifter deflecting surface, a layer oftetrofluorethylene lubricant on said surface, a cantilever supportedcontact lifter of spring metal having a surface in contact with saidlayer, means directly connecting said reed and lifter electricallytogether, a contact surface on said lifter, and means providing a fixedcontact surface opposite said contact surface.

References Cited in the file of this patent UNITED STATES PATENTSVazquez Sept. 18, 1956 2,790,129 Barnes Apr. 23, 1957 2,859,299 HowellNov. 4, 1958

